With the increasing development of internetwork and information techniques, a mobile terminal changes from a simple audio communication tool to a comprehensive information processing platform integrating entertainment and practicability. An existing mobile terminal not only has functions for audio communication and text messaging, but also supports multimedia function, multimedia messaging service, Internet service and multiple Java programs, providing great convenience to people's modern life.
Since a touch panel has advantages of being sturdy and durable, responsive, space-saving and convenient to implement human-computer interaction, thus it is widely used in various mobile terminals such as a mobile phone, a digital photo frame, a Personal Digital Assistant (PDA), a tablet computer and the like, and replaces gradually a traditional display screen of a mobile terminal. Through a touch panel, functions of a physical keyboard can be simulated, and an Organic Light-Emitting Diode (OLED) display panel is arranged under the touch panel to display key labels. With the application of a touch panel, physical keys of a mobile terminal become fewer and fewer, functions of physical keys are gradually replaced by those of a touch panel, but certain keys of the mobile terminal are not yet replaced, such as Home (main page) key, return key and volume key, therefore there are some area needed to arrange keys on the mobile terminal.
At present, a mobile terminal tends to become thinner and thinner in thickness and larger and larger in screen size, but since keys of a mobile terminal may occupy some area, the thickness and screen size thereof are limited with the volume of the mobile terminal being fixed.